In the course of operating a folding apparatus, the front or leading end sections of signatures are speared or impaled on the spur needles of a spur strip which is carried by a spur cylinder or a puncture cylinder. The speared, impaled or spurred signatures are drawn by the rotating spur cylinder through a transfer gap which is formed by the spur cylinder and by a cooperating folding jaw cylinder which has been placed against the spur cylinder. In the transfer gap, a signature is grasped by the folding jaws of the folding jaw cylinder. At the same time, the spur strip is pivoted into its recessed position and in this way releases the signature. Upon its release from the spur strip, the front portion of the released signature slides across a shell face of the spur cylinder opposite to the direction of rotation of the spur cylinder. In the course of this, the danger arises that this signature front portion, as it passes over following spur needles of a further or, depending on the circumference of the spur cylinder, the same spur strip, on which a second signature has been speared, will be damaged by them. The danger of damage to the signature is particularly great in connection with delta folding production. In this case, approximately two-thirds of a portion of the signature is located in front of the folding blade, and one third of a portion of the signature is located behind the folding blade.
A spur cylinder with additional grippers, which act on the leading edge of the signature, is known from DE 43 40 585 C2. Since, in that device, the spur needles are retracted after the additional grippers have made contact, the danger of damage being done to the removed signature by subsequent spur needles does not occur.
DE 100 18 775 A1, DE 21 26 610 A1 and DE 20 25 347 A1 all disclose strippers for use in lifting signatures off the spur needles. A protective function is not provided by these devices, since these strippers act from below the speared signature.
EP 0 019 202 A1 discloses a spur cylinder with spur coverings. No detailed information regarding possible positions or movements of these spur coverings is provided.